Ask HN: Does anyone have any experience with civil/env. engineering startups?

I'm a software developer that works for an engineering firm. A few of us here are thinking about creating a civil/environmental engineering startup. Naturally, a startup in this field would have some differences to a company focusing on web development. Does anyone on HN have any experience in this area? How did you go about landing clients in the beginning? Were there any pitfalls that I should be aware of?